To radiate heat generated by a semiconductor device, a heat sink is attached to the semiconductor device, or the semiconductor device is fixed to a heat sink with a submount made of a material having a high thermal conductivity being interposed between them.
Patent reference 1 describes that it is favorable to use GaN (gallium nitride) as the material of the heat sink or submount, and that the thermal conductivity of the material is preferably 100 to 300 (W/m·K) within the range of 0 to 200 (° C.). However, patent reference 1 does not disclose any practical method of manufacturing a GaN member having a thermal conductivity of 100 to 300 (W/m·K) within the range of 0 to 200 (° C.). Also, patent reference 1 does not describe that GaN having a thermal conductivity of 100 to 300 (W/m·K) was obtained.
Non-patent reference 1 describes the dependence of the thermal conductivity of GaN on the temperature. According to non-patent reference 1, the thermal conductivity of GaN is 1.7 (W/cm·K) at 300 (K).
Non-patent reference 2 describes that the thermal conductivity of oxygen-doped GaN was 225 (W/m-K) when measured at room temperature (the measurement method was the 30) method). Non-patent reference 2 also describes that the theoretical limit of the thermal conductivity of an ideal GaN crystal is 410 (W/m·K).
Non-patent reference 3 describes that the thermal conductivity of a GaN substrate manufactured by Cree is 220 (W/m·K) at room temperature (the measurement method is the laser flash method).
Patent reference 1: Japanese Patent Laid-Open No. 2003-78084
Non-patent reference 1: J. Phys. Chem. Solids, 1977, Vol. 38, p. 330
Non-patent reference 2: phys. Stat. sol. (a) 202, No. 12, R135-R137 (2005)
Non-patent reference 3: [Searched Dec. 22, 2005], Internet <URL:http://www.cree.com/products/gan_tech.htm>